Electrical transformers are large devices that are typically cooled and insulated by mineral oil. Many such transformers, large power, pad-mounted and pole-mounted, are used in the electric power industry. The mineral oil serves as a coolant and also suppresses corona and arcing and insulates various internal electrically energized parts. Since transformer oils are subject to electrical, thermal and mechanical stresses while a transformer is in operation, as well as being contaminated by chemical interactions with copper or aluminum windings and other solid insulation, it is important to test the oil regularly to ensure the continued operability of the transformer and the effectiveness of the oil. Such testing can measure the amount of dissolved gas in the oil that has emulsified during adverse operating conditions, various contaminants present in the oil, or any other indications of sparking, wear, high temperatures, or other transformer damage caused by environmental conditions.
Typically, the oil tank on a transformer has a large valve close to the bottom of the tank. To test the oil, a worker has to open the valve and fill a sample container with oil; the sample container is then taken to a laboratory to be tested. The sample containers comprise of a metal or plastic valve that allows the oil to flow in but prevents it from flowing out. These containers are common syringe design, constructed of glass.
This method has several problems. The oil in a transformer tends to contain sediment that settles close to the bottom of the tank. To draw out a usable sample, a worker has to flush the system sufficiently that the sample is free of sediment and contaminants. This results in a lot of oil being simply wasted, and a much lengthier, more expensive, and more complicated process for taking the sample. The fact that each container, glass or metal has to incorporate a valve in the cap and makes the containers more expensive as well. Due to the expense and complexity of the process, many transformers are simply not tested at all, which has negative impact to the equipment's reliability and is dangerous.
A need therefore exists for a simpler, quicker, and less expensive system and method for taking oil samples from a transformer.